The present invention relates to a tape-mounted snap fastener having engagement and disengagement directionality. When male and female parts of this type of fastener are provided on two separate fabrics, the fabrics can be disengaged only from a certain direction and not from other directions. This kind of snap fastener having such a directionality can be used in a variety of applications including clothing, bags and shoes.
The present applicant has developed and made patent applications for snap fasteners of this kind having disengagement directionality.
For example, the invention disclosed in JP-A-10-33210 (1998) is a tape-mounted snap fastener with tapes comprising a male-side tape consisting of resin male snap parts mould-fastened on a cloth tape at free intervals and a female-side tape consisting of resin female snap parts mould-fastened on a cloth tape at free intervals, using a resin-molding means. The male snap part has an attachment protrusion sticking out from the center of a male base part, said attachment protrusion comprising a neck part and an attachment head, wherein said neck part is concentric with the male base part while said attachment head is eccentric from the axial center of the neck part to form an engagement edge. The female snap part has a female base part having a head-inserting guide hole for inserting the attachment protrusion, an attachment hole through which the attachment head passes as it elastically changes its form, and a head chamber hole encasing the attachment head, wherein said head-inserting guide hole is concentric with the attachment hole while said head chamber hole is eccentric from the insertion center so as to correspond to the eccentricity of the attachment head of the male snap part, and a stopper step is formed at least on the eccentric side of the periphery of the head chamber hole. The attachment strength of this snap fastener differs depending on the direction in which it is pulled apart.
In the invention of the above application, directionality appears when the male snap part and the female snap part are disengaged, but there is no directionality when they are engaged. There is an advantage to this arrangement in that the male and female parts can be engaged to each other without any sense of obstruction, but it also makes the user apt to forget the directionality in which the snap fastener can be pulled apart. If the user attempts to pull apart the male and female sides in directions in which they are difficult to separate, the fabrics on which the snap parts are attached can be damaged.
The object of the present invention is to provide a snap fastener that has directionality not only for disengagement but also for engagement.
The tape-mounted snap fastener having an engagement and disengagement directionality according to the present invention comprises a male tape and a female tape in which the male tape consists of a cloth tape on which several synthetic resin male parts are molded and fastened at certain intervals and the female tape consists of a cloth tape on which several synthetic resin female parts are molded and fastened at certain intervals, characterized in that from the xe2x80x9cfacexe2x80x9d side of the base of the male part the engagement protrusion extends diagonally upwards in the direction of the engagement socket, while a slanting surface parallel with the protrusion-forming slanting surface is formed within the engagement socket, on the xe2x80x9cfacexe2x80x9d side of the base, and from the xe2x80x9cfacexe2x80x9d side of the base of the female part the engagement protrusion extends diagonally downwards in the direction of the engagement socket, while a slanting surface parallel with the protrusion-forming slanting surface is formed within the engagement socket, on the xe2x80x9cfacexe2x80x9d side of the base, forming the space for housing the male part engagement protrusion when the male and female parts are engaged.
Preferably, the protrusion-forming slanting surface on the engagement socket side of the male part is provided with a small protrusion, and the protrusion-forming slanting surface on the engagement socket side of the female part is provided with a step. In this way, the small protrusion of the male part engages with the step of the female part when the male and female parts are completely engaged.
The slant angle of the protrusion-forming slanting surfaces of the male and female parts is from 30 to 60 degrees, and preferably 45 degrees.
The heads of the engagement protrusions of the male and female parts are preferably arranged parallel with their respective cloth tapes in order to make the snap as thin as possible.
At least one of the male and female parts is preferably provided with a mark that indicates the directionality of the engagement.
According to the present invention, the male part and the female part engage or disengage in such a way that they slide on their respective protrusion-forming slanting surfaces. Therefore, the snap fastener of the present invention has directionality not only for disengaging the male and female parts but also for engaging them. Moreover, when they are completely engaged, the small protrusion of the male part sits on the step of the female part to stabilize the engagement.